Shenyang FC-31 / J-31 Fighter Demonstrator

Air Force Brat · Nov 22, 2017

by78 said:
Before this gets out of hand, the video never said the reduction was 26.7%. Rather, as latenlazy pointed out, for an unnamed Shenyang aircraft, the ratio of its structural weight to its takeoff weight is 26.7%. The original video stated that it's optimal that an aircraft's structural weight be capped at 30% of its takeoff weight. Achieving a 28% ratio is considered very good, and with Shenyang's 3D printing techniques, they were able to shave the ratio down to 26.7%.

You're figures are backward, the empty aircraft will weigh somewhere around 65% to 75% of its designed Max gross weight, but 3D printing does indeed result in significant weight savings, as I stated previously 3% to 7%, with my best guestimation for the FC-31/J-20 likely running in around the 5% range..

It may get better as time goes on, a 10% weight savings would be huge in any aircraft class, and it would be the talk of the aircraft industry,,,,, but we haven't heard anybody even suggesting a world changing number like that, on an aircraft that's currently in production.

vesicles · Nov 22, 2017

Air Force Brat said:
You're figures are backward, the empty aircraft will weigh somewhere around 65% to 75% of its designed Max gross weight, but 3D printing does indeed result in significant weight savings, as I stated previously 3% to 7%, with my best guestimation for the FC-31/J-20 likely running in around the 5% range..

It may get better as time goes on, a 10% weight savings would be huge in any aircraft class, and it would be the talk of the aircraft industry,,,,, but we haven't heard anybody even suggesting a world changing number like that, on an aircraft that's currently in production.

I think you might be over estimating the weight loss. My understanding is that they are only focusing on the structural part of the empty plane and shave off about 3% of that.

Based on what I can understand from the interview, if let’s say the J-20 initially weighs 20 tons, that would make its structural part at ~6 tons (based on the 30% estimate by the engineer in the clip). If they shave off ~3% of that, that would make the total lost weight at 0.18 tons. That would make the weight loss to be ~1% of the total empty weight of the entire plane. So now the new J-29 would weigh 19.82. My interpretation of the clip...

manqiangrexue · Nov 22, 2017

Air Force Brat said:
No it won't, and yes I am smirking,,, Happy Thanksgiving Brother, and may all of God's Blessings and Love fall on you, and all of my Sino Defense Bros, I do love you guys, yep even you brother.

but dreaming that the J-31 or J-20 weigh 25% less than their contemporaries is just a fan-tasy, and you're right, if it did that would be amazing, but no matter how you close your eyes and wish, or hold your breath, the J-20 is still probably gonna be heavier than the F-22!

Well, last time I closed my eyes and wished for a Chinese supercomputer to be number 1, it happened. This time, the problem is, they ain't allowed to tell you that it happened.

Now then, we do have a dilemma. I just took a look at the video this morning since I was looking at the screenshots yesterday. They are talking about J-15; they said that normally, the structural weight of the aircraft is ~30% of the "take off weight." But with 3D printing, they got J-15 to 26.8%. Now the problem is, they never clarified what "take off weight" means. Does it mean empty weight? Or standard load? Or full load? Or MTOW?

So, in your experience, which I'm referring to for the first time, which of these definitions makes sense? Is an aircraft's structural weight usually 30% of empty weight, or standard load, or max load or MTOW? Everyone is dying to know after seeing that clip.

manqiangrexue · Nov 22, 2017

vesicles said:
I think you might be over estimating the weight loss. My understanding is that they are only focusing on the structural part of the empty plane and shave off about 3% of that.

Based on what I can understand from the interview, if let’s say the J-20 initially weighs 20 tons, that would make its structural part at ~6 tons (based on the 30% estimate by the engineer in the clip). If they shave off ~3% of that, that would make the total lost weight at 0.18 tons. That would make the weight loss to be ~1% of the total empty weight of the entire plane. So now the new J-29 would weigh 19.82. My interpretation of the clip...

Yeah, the screen shots were deceiving. I thought they were talking about J-31 but actually, the entire interview was about making micro-improvements to a mature J-15 design. J-31 just happened to be in the background.

Doesn't apply to J-20 though, cus it's a new design with greatly increased composite use. 3D printing is really just 1 of many weight-saving tactics though it's most commonly referred to since it's most well-known.

In either case, 787 supposedly saved 20% weight by using greater composites and other techniques. This at least doesn't disprove J-20 at 15-16 tonnes. It was simply a false alarm (started by me) cus it was late and I just looked at the screen shots ignoring the 30 min video that was actually on adjusting the J-15.

B.I.B. · Nov 22, 2017

vesicles said:
It sounds to me that your initial interpretation was good. They managed to decrease the structural weight from 28% to 26.8% of the total weight of the plane.

When the interviewer made a comment that the decrease might sound a little trivial, the engieneer said that, on a fighter, cutting down even one gram is very significant.

In that case you can use lighter built pilots,maybe even jockey sized.Afterall they should not be referred to as fighter jocks for nothing.

b787 · Nov 22, 2017

manqiangrexue said:
In either case, 787 supposedly saved 20% weight by using greater composites and other techniques.

this is compared to an old B-707 or B-727 or any airliner made of mostly of aluminium, like those Tu-154, compared to a modern airliner, well no weight saving like A-350.

Composites have ben used more extensively since 1977 in Russia for example MiG-29, but is very likely F-22 and F-35 use a much larger proportion, but still, due to the fact Stealth aircraft have bigger fuselages, wings etc etc due to internal storage such as weapons bays, the F-35 is 2 tonnes heavier than MiG-29 and 4 tonnes heavier than F-16.
Even PAKFA that uses more composites than Su-27 weights more than any Flanker at empty weigh.

F-22 uses more composites than F-15 and weights 6 tonnes more than the Eagle at empty weight and have a comparable length.

JF-31 must weigh around 13 tonnes like F-35, perhaps slightly heavier or lighter, but mostly marginally, F-22 is heavier due to its 2D nozzles which add 1 ton just its fuselage wise is around 18 tons so you can really expect for J-20 with all the advances a realistic weight in the range of 18.5-20.5 tons at empty weight, because volumetrically is much bigger than F-22 but has Al-31 much lighter than F-119

manqiangrexue · Nov 22, 2017

b787 said:
this is compared to an old B-707 or B-727 or any airliner made of mostly of aluminium, like those Tu-154, compared to a modern airliner, well no weight saving like A-350.

Composites have ben used more extensively since 1977 in Russia for example MiG-29, but is very likely F-22 and F-35 use a much larger proportion, but still, due to the fact Stealth aircraft have bigger fuselages, wings etc etc due to internal storage such as weapons bays, the F-35 is 2 tonnes heavier than MiG-29 and 4 tonnes heavier than F-16.
Even PAKFA that uses more composites than Su-27 weights more than any Flanker at empty weigh.

F-22 uses more composites than F-15 and weights 6 tonnes more than the Eagle at empty weight and have a comparable length.

JF-31 must weigh around 13 tonnes like F-35, perhaps slightly heavier or lighter, but mostly marginally, F-22 is heavier due to its 2D nozzles which add 1 ton just its fuselage wise is around 18 tons so you can really expect for J-20 with all the advances a realistic weight in the range of 18.5-20.5 tons at empty weight, because volumetrically is much bigger than F-22 but has Al-31 much lighter than F-119

Where did you ascertain that Dreamliner's 20% savings were from 707 or 727? I don't think they ever said that was their comparison standard. I think they mean 20% savings over if the same design was made but with conventional materials.

Comparing 5th gen to 4th gen is not going to get anybody anywhere. 5th gens have that internal bay and a layer of RAM to consider (which by itself, could weigh a few tons as calculated before, who knows?).

LOL Let's not get into guessing the J-31 weight without any information here, ok? We haven't gotten anywhere with the J-20 weight despite there being a report of it's weight (causing some people to revise their initial estimate down some random, incalculable amount). We literally don't have anything on J-31.

b787 · Nov 22, 2017

manqiangrexue said:
Where did you ascertain that Dreamliner's 20% savings were from 707 or 727? I don't think they ever said that was their comparison standard. I think they mean 20% savings over if the same design was made but with conventional materials.

Comparing 5th gen to 4th gen is not going to get anybody anywhere. 5th gens have that internal bay and a layer of RAM to consider (which by itself, could weigh a few tons as calculated before, who knows?).

LOL Let's not get into guessing the J-31 weight without any information here, ok? We haven't gotten anywhere with the J-20 weight despite there being a report of it's weight (causing some people to revise their initial estimate down some random, incalculable amount). We literally don't have anything on J-31.

Composites have been used just recently, most older airliners are made mostly of aluminium

As the graph shows B-747 was a 1970s design, like B-727, even the 1990s B-777 did not use as much as B-787

The MiG-29 if compared to a F-22, it is 8 tonnes lighter than F-22 it weighs 11 tons at empty weight, and it is more than 2 tons lighter than F-35.

If B-787 is made mostly of aluminium, it will be comparable to a VC-10 or Il-62 in aircraft type, J-31 will not be as light as MiG-29 at empty weight, and it is easy to see, MiG-29 weighs at least 10 tons lighter than J-31 atMax take off, even the modern MiG-35 is much lighter than J-31 at 28 tons max takeoff weight.

F-35 weighs almost 30 tons at max weight, do you expect the J-31 to weight 18 tons like a MiG-29? be my guest, and continue with the Fan-tasy

Table 1. Contrast in material application proportions of F-15, F/A-22 fighter and B-2 bomber. Type Aluminum alloy Titanium alloy Alloy steel Composite materials Other materials

F-15 0.50 0.34 0.02 0.02 0.12

F/A-22 0.15 0.40 0.06 0.34 0.05
B-2 0.24 0.18 0.1 0.38 0.01

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The F-22 is 34% composites compared to a 1970s F-15 that is only 2%

manqiangrexue · Nov 22, 2017

b787 said:
Composites have been used just recently, most older airliners are made mostly of aluminium

As the graph shows B-747 was a 1970s design, like B-727, even the 1990s B-777 did not use as much as B-787

The MiG-29 if compared to a F-22, it is 8 tonnes lighter than F-22 it weighs 11 tons at empty weight, and it is more than 2 tons lighter than F-35.

If B-787 is made mostly of aluminium, it will be comparable to a VC-10 or Il-62 in aircraft type, J-31 will not be as light as MiG-29 at empty weight, and it is easy to see, MiG-29 weighs at least 10 tons lighter than J-31 atMax take off, even the modern MiG-35 is much lighter than J-31 at 28 tons max takeoff weight.

F-35 weighs almost 30 tons at max weight, do you expect the J-31 to weight 18 tons like a MiG-29, be my guest, and continue with the Fan-tasy

This entire conversation is your fantasy. Nobody here except you is guessing the weight of J-31 because there is no evidence. You're quoting my comment but you're not talking to me because I never said anything about J-31 weight. 10 tons, 18 tons, 28 tons, 30 tons, I didn't say any of that; they are all your mental fabrication cus making up numbers with no evidence is your specialty.

b787 · Nov 22, 2017

manqiangrexue said:
This entire conversation is your fantasy. Nobody here except you is guessing the weight of J-31 because there is no evidence. You're quoting my comment but you're not talking to me because I never said anything about J-31 weight. Making up numbers with no evidence is your fantasy and you're famous for it here.

I will give you a riddle, why if F-22 has 34% of its structure made of composites, compared to the 50% aluminium made F-15 that only has 2% of its structure of composites, why the F-15 Eagle at empty weight weighs 13 tonnes like F-35, and F-22 weighs 19.8 tonnes, Why?

Shenyang FC-31 / J-31 Fighter Demonstrator

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